/*!
 * Ext JS Library 3.1.0
 * Copyright(c) 2006-2009 Ext JS, LLC
 * licensing@extjs.com
 * http://www.extjs.com/license
 */
Ext.ns('Ext.ux.grid');

/**
 * @class Ext.ux.grid.BufferView
 * @extends Ext.grid.GridView
 * A custom GridView which renders rows on an as-needed basis.
 */
Ext.ux.grid.BufferView = Ext.extend(Ext.grid.GridView, {
    /**
     * @cfg {Number} rowHeight
     * The height of a row in the grid.
     */
    rowHeight: 19,

    /**
     * @cfg {Number} borderHeight
     * The combined height of border-top and border-bottom of a row.
     */
    borderHeight: 2,

    /**
     * @cfg {Boolean/Number} scrollDelay
     * The number of milliseconds before rendering rows out of the visible
     * viewing area. Defaults to 100. Rows will render immediately with a config
     * of false.
     */
    scrollDelay: 100,

    /**
     * @cfg {Number} cacheSize
     * The number of rows to look forward and backwards from the currently viewable
     * area.  The cache applies only to rows that have been rendered already.
     */
    cacheSize: 20,

    /**
     * @cfg {Number} cleanDelay
     * The number of milliseconds to buffer cleaning of extra rows not in the
     * cache.
     */
    cleanDelay: 500,

    initTemplates: function () {
        Ext.ux.grid.BufferView.superclass.initTemplates.call(this);
        var ts = this.templates;
        // empty div to act as a place holder for a row
        ts.rowHolder = new Ext.Template(
            '<div class="x-grid3-row {alt}" style="{tstyle}"></div>'
        );
        ts.rowHolder.disableFormats = true;
        ts.rowHolder.compile();

        ts.rowBody = new Ext.Template(
            '<table class="x-grid3-row-table" border="0" cellspacing="0" cellpadding="0" style="{tstyle}">',
            '<tbody><tr>{cells}</tr>',
            (this.enableRowBody ? '<tr class="x-grid3-row-body-tr" style="{bodyStyle}"><td colspan="{cols}" class="x-grid3-body-cell" tabIndex="0" hidefocus="on"><div class="x-grid3-row-body">{body}</div></td></tr>' : ''),
            '</tbody></table>'
        );
        ts.rowBody.disableFormats = true;
        ts.rowBody.compile();
    },

    getStyleRowHeight: function () {
        return Ext.isBorderBox ? (this.rowHeight + this.borderHeight) : this.rowHeight;
    },

    getCalculatedRowHeight: function () {
        return this.rowHeight + this.borderHeight;
    },

    getVisibleRowCount: function () {
        var rh = this.getCalculatedRowHeight();
        var visibleHeight = this.scroller.dom.clientHeight;
        return (visibleHeight < 1) ? 0 : Math.ceil(visibleHeight / rh);
    },

    getVisibleRows: function () {
        var count = this.getVisibleRowCount();
        var sc = this.scroller.dom.scrollTop;
        var start = (sc == 0 ? 0 : Math.floor(sc / this.getCalculatedRowHeight()) - 1);
        return {
            first: Math.max(start, 0),
            last: Math.min(start + count + 2, this.ds.getCount() - 1)
        };
    },

    doRender: function (cs, rs, ds, startRow, colCount, stripe, onlyBody) {
        var ts = this.templates, ct = ts.cell, rt = ts.row, rb = ts.rowBody, last = colCount - 1;
        var rh = this.getStyleRowHeight();
        var vr = this.getVisibleRows();
        var tstyle = 'width:' + this.getTotalWidth() + ';height:' + rh + 'px;';
        // buffers
        var buf = [], cb, c, p = {}, rp = {tstyle: tstyle}, r;
        for (var j = 0, len = rs.length; j < len; j++) {
            r = rs[j];
            cb = [];
            var rowIndex = (j + startRow);
            var visible = rowIndex >= vr.first && rowIndex <= vr.last;
            if (visible) {
                for (var i = 0; i < colCount; i++) {
                    c = cs[i];
                    p.id = c.id;
                    p.css = i == 0 ? 'x-grid3-cell-first ' : (i == last ? 'x-grid3-cell-last ' : '');
                    p.attr = p.cellAttr = "";
                    p.value = c.renderer(r.data[c.name], p, r, rowIndex, i, ds);
                    p.style = c.style;
                    if (p.value == undefined || p.value === "") {
                        p.value = "&#160;";
                    }
                    if (r.dirty && typeof r.modified[c.name] !== 'undefined') {
                        p.css += ' x-grid3-dirty-cell';
                    }
                    cb[cb.length] = ct.apply(p);
                }
            }
            var alt = [];
            if (stripe && ((rowIndex + 1) % 2 == 0)) {
                alt[0] = "x-grid3-row-alt";
            }
            if (r.dirty) {
                alt[1] = " x-grid3-dirty-row";
            }
            rp.cols = colCount;
            if (this.getRowClass) {
                alt[2] = this.getRowClass(r, rowIndex, rp, ds);
            }
            rp.alt = alt.join(" ");
            rp.cells = cb.join("");
            buf[buf.length] = !visible ? ts.rowHolder.apply(rp) : (onlyBody ? rb.apply(rp) : rt.apply(rp));
        }
        return buf.join("");
    },

    isRowRendered: function (index) {
        var row = this.getRow(index);
        return row && row.childNodes.length > 0;
    },

    syncScroll: function () {
        Ext.ux.grid.BufferView.superclass.syncScroll.apply(this, arguments);
        this.update();
    },

    // a (optionally) buffered method to update contents of gridview
    update: function () {
        if (this.scrollDelay) {
            if (!this.renderTask) {
                this.renderTask = new Ext.util.DelayedTask(this.doUpdate, this);
            }
            this.renderTask.delay(this.scrollDelay);
        } else {
            this.doUpdate();
        }
    },

    onRemove: function (ds, record, index, isUpdate) {
        Ext.ux.grid.BufferView.superclass.onRemove.apply(this, arguments);
        if (isUpdate !== true) {
            this.update();
        }
    },

    doUpdate: function () {
        if (this.getVisibleRowCount() > 0) {
            var g = this.grid, cm = g.colModel, ds = g.store;
            var cs = this.getColumnData();

            var vr = this.getVisibleRows();
            for (var i = vr.first; i <= vr.last; i++) {
                // if row is NOT rendered and is visible, render it
                if (!this.isRowRendered(i)) {
                    var html = this.doRender(cs, [ds.getAt(i)], ds, i, cm.getColumnCount(), g.stripeRows, true);
                    this.getRow(i).innerHTML = html;
                }
            }
            this.clean();
        }
    },

    // a buffered method to clean rows
    clean: function () {
        if (!this.cleanTask) {
            this.cleanTask = new Ext.util.DelayedTask(this.doClean, this);
        }
        this.cleanTask.delay(this.cleanDelay);
    },

    doClean: function () {
        if (this.getVisibleRowCount() > 0) {
            var vr = this.getVisibleRows();
            vr.first -= this.cacheSize;
            vr.last += this.cacheSize;

            var i = 0, rows = this.getRows();
            // if first is less than 0, all rows have been rendered
            // so lets clean the end...
            if (vr.first <= 0) {
                i = vr.last + 1;
            }
            for (var len = this.ds.getCount(); i < len; i++) {
                // if current row is outside of first and last and
                // has content, update the innerHTML to nothing
                if ((i < vr.first || i > vr.last) && rows[i].innerHTML) {
                    rows[i].innerHTML = '';
                }
            }
        }
    },

    layout: function () {
        Ext.ux.grid.BufferView.superclass.layout.call(this);
        this.update();
    }
});
